Generally, when a diaphragm provided in an imaging lens system is set on an open aperture side, oblique incident light cannot enter each of pixels (photodiodes) of a solid-state imaging device (image sensor) sufficiently, thereby causing deterioration of sensitivity of the solid-state imaging device. That is, the sensitivity of the solid-state imaging device has a characteristic depending on the F-number of the imaging lens.
This is because there is a distance between a light incidence surface of each photodiode formed in a semiconductor substrate and a micro-lens formed thereabove, for example, as described in the following Patent Literatures 1 and 2. That is, even when oblique incident light enters the micro-lens in the upper layer, the incident light cannot reach the photodiode in the lower layer sufficiently.
For this reason, when an image of a photographic subject is taken by an imaging apparatus, data of the image of the photographic subject are corrected based on information about F-number dependence of sensitivity of a solid-state imaging device mounted in the imaging apparatus.